diff --git a/src/os2/region.cpp b/src/os2/region.cpp
index 2e65b85d01..c742b392a4 100644
--- a/src/os2/region.cpp
+++ b/src/os2/region.cpp
@@ -225,7 +225,7 @@ wxObjectRefData *wxRegion::CreateData() const
     return new wxRegionRefData;
 }
 
-wxObjectRefData *wxRegion::CloneData(wxObjectRefData *data) const
+wxObjectRefData *wxRegion::CloneData(const wxObjectRefData *data) const
 {
     return new wxRegionRefData(*(wxRegionRefData *)data);
 }